Application of image correction techniques to images is well known. One particular area of image correction is distortion correction, which is concerned with correcting distortions or spatial abnormalities in an image, such as stretching, warping, skewing, or rotation. The two major sources of distortion are the nature of the lens used in the camera, and manufacturing abnormalities in the camera. The nature of the lens may distort the image, for example, when a wide-angle lens is utilized, thus creating a “fish-eye” type distortion in the image, such that the portions of the image located at the sides and corners of the image appear compressed while the center of the image appears expanded. Also, manufacturing abnormalities in a particular camera may arise from misalignment of the components of the camera, or from abnormalities in a particular portion of the camera. Although manufacturing abnormalities may be reduced or eliminated by specifying precise tolerances for the camera, doing so increases production costs, which is undesirable.
Distortions may be corrected, generally speaking, by shifting or stretching an image to mitigate the distortion. However, manual distortion correction is time consuming, and is not suitable for application to a real time video signal. One way in which distortions in a real-time video image may be corrected is by applying a spatial transformation to the image using a pre-determined calibration table, which causes portions of the image to be shifted, compressed, or expanded in a pre-determined manner, often on a pixel-by-pixel basis. These systems contemplate use of a pre-determined calibration table that is produced for use with an entire family of cameras. However, use of a pre-determined calibration table that was not developed using the camera to which the calibration is being applied is only feasible if the images produced by the two cameras are substantially similar, and thus distorted in a similar manner. Otherwise, application of the distortion correction to the image could result in a further distorted image. Thus, these systems require cameras that produce images that are distorted in a substantially similar manner, thereby requiring precise manufacturing of the cameras to stringent design tolerances. Furthermore, a new calibration table must be developed to accommodate changes in the camera being used for the application.